wait for transmitter to be done before receiving
At higher speeds, it seems we are turning off the transmitter before we
are enabling the receiver. Unfortunately the TXEN bit in the uart mode
register is read-only, so we don't really know if the transmitter is
enabled or not. It seems we can simply keep transmitter + reciver
running at the same time, and use the TXEMPTY bit as reliable means to
determine if we're busy transmtting.
diff --git a/firmware/src_simtrace/mode_cardemu.c b/firmware/src_simtrace/mode_cardemu.c
index c012701..098e0d6 100644
--- a/firmware/src_simtrace/mode_cardemu.c
+++ b/firmware/src_simtrace/mode_cardemu.c
@@ -84,6 +84,19 @@
* Call-Backs from card_emu.c
***********************************************************************/
+static void wait_tx_idle(Usart *usart)
+{
+ int i = 1;
+
+ /* wait until last char has been fully transmitted */
+ while ((usart->US_CSR & (US_CSR_TXEMPTY)) == 0) {
+ if (!(i%1000000)) {
+ TRACE_ERROR("s: %x \r\n", usart->US_CSR);
+ }
+ i++;
+ }
+}
+
/* call-back from card_emu.c to enable/disable transmit and/or receive */
void card_emu_uart_enable(uint8_t uart_chan, uint8_t rxtx)
{
@@ -91,14 +104,19 @@
switch (rxtx) {
case ENABLE_TX:
USART_DisableIt(usart, ~US_IER_TXRDY);
- USART_SetReceiverEnabled(usart, 0);
+ /* as irritating as it is, we actually want to keep the
+ * receiver enabled during transmit */
+ USART_SetReceiverEnabled(usart, 1);
usart->US_CR = US_CR_RSTSTA | US_CR_RSTIT | US_CR_RSTNACK;
USART_EnableIt(usart, US_IER_TXRDY);
USART_SetTransmitterEnabled(usart, 1);
break;
case ENABLE_RX:
USART_DisableIt(usart, ~US_IER_RXRDY);
- USART_SetTransmitterEnabled(usart, 0);
+ /* as irritating as it is, we actually want to keep the
+ * transmitter enabled during receive */
+ USART_SetTransmitterEnabled(usart, 1);
+ wait_tx_idle(usart);
usart->US_CR = US_CR_RSTSTA | US_CR_RSTIT | US_CR_RSTNACK;
USART_EnableIt(usart, US_IER_RXRDY);
USART_SetReceiverEnabled(usart, 1);